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Jesus · 06-22-2008, 12:40 AM

Since my post of yesterday (#29 on this thread), I have come across one more article that clearly discusses the genetic component of male homosexuality. It ought to be published some time this summer and is not yet on line.

Iemmola and Ciani discuss their research on 250 Italian men (152 of them homosexual) and their extended families. The evidence is very strong for a genetic component, one gene of which is on the X chromosome. In females, the genes produce women who have significantly larger numbers of children than those women who do not carry the genes.

In the Discussion section of the article, they also note that gay males in their study had a statistically significantly larger number of older brothers than did straight males. There was no significant difference in the numbers of other sibling types – older sisters, younger brothers, younger sisters. This would fit with the additional environmental factor of having been born from a womb that had already nurtured males and that there is some sort of hormonal factor involved.

+++++++

Francesca Iemmola and Andrea Camperio Ciani (2008) New Evidence of Genetic Factors Influencing Sexual Orientation in Men: Female Fecundity Increase in the Maternal Line. Archives of Sexual Behavior, IN PRESS - DOI 10.1007/s10508-008-9381-6

ABSTRACT: “There is a long-standing debate on the role of genetic factors influencing homosexuality because the presence of these factors contradicts the Darwinian prediction according to which natural selection should progressively eliminate the factors that reduce individual fecundity and fitness. Recently, however, Camperio Ciani, Corna, and Capiluppi (Proceedings of the Royal Society of London, Series B: Biological Sciences, 271, 2217–2221, 2004), comparing the family trees of homosexuals with heterosexuals, reported a significant increase in fecundity in the females related to the homosexual probands from the maternal line but not in those related from the paternal one. This suggested that genetic factors that are partly linked to the X-chromosome and that influence homosexual orientation in males are not selected against because they increase fecundity in female carriers, thus offering a solution to the Darwinian paradox and an explanation of why natural selection does not progressively eliminate homosexuals. Since then, new data have emerged suggesting not only an increase in maternal fecundity but also larger paternal family sizes for homosexuals. These results are partly conflicting and indicate the need for a replication on a wider sample with a larger geographic distribution. This study examined the family trees of 250 male probands, of which 152 were homosexuals. The results confirmed the study of Camperio Ciani et al. (2004). We observed a significant fecundity increase even in primiparous mothers, which was not evident in the previous study. No evidence of increased paternal fecundity was found; thus, our data confirmed a sexually antagonistic inheritance partly linked to the X-chromosome that promotes fecundity in females and a homosexual sexual orientation in males.”

From the DISCUSSION: “Blanchard’s predictions were also confirmed in our study: we found that the homosexuals had an excess of older brothers compared with their own number of older sisters and compared with the heterosexuals’ number of older brothers. The homosexual and heterosexual groups did not differ with regard to the other three classes of siblings.”

+++++++

Homosexuality clearly is caused by multiple factors, both genetic and environmental. It’s persistence in the species argues strongly that it provides some sort of reproductive advantage to those sharing the genes of the gay male involved. Remember that you are as closely related, genetically, to your nieces and nephews as you are to your grandchildren – sharing ¼ of your genes with both. Having more successful nieces and nephews is, reproductively, the same as having more successful grandchildren.

Being gay may be a sign that your family line carries one significant genetic advantage over lines that do not have gay males.

06-22-2008, 12:40 AM	#35
Jesus agent provocateur Join Date: Feb Sat 2001 Posts: 2,329	Re: What does gay look like? Since my post of yesterday (#29 on this thread), I have come across one more article that clearly discusses the genetic component of male homosexuality. It ought to be published some time this summer and is not yet on line. Iemmola and Ciani discuss their research on 250 Italian men (152 of them homosexual) and their extended families. The evidence is very strong for a genetic component, one gene of which is on the X chromosome. In females, the genes produce women who have significantly larger numbers of children than those women who do not carry the genes. In the Discussion section of the article, they also note that gay males in their study had a statistically significantly larger number of older brothers than did straight males. There was no significant difference in the numbers of other sibling types – older sisters, younger brothers, younger sisters. This would fit with the additional environmental factor of having been born from a womb that had already nurtured males and that there is some sort of hormonal factor involved. +++++++ Francesca Iemmola and Andrea Camperio Ciani (2008) New Evidence of Genetic Factors Influencing Sexual Orientation in Men: Female Fecundity Increase in the Maternal Line. Archives of Sexual Behavior, IN PRESS - DOI 10.1007/s10508-008-9381-6 ABSTRACT: “There is a long-standing debate on the role of genetic factors influencing homosexuality because the presence of these factors contradicts the Darwinian prediction according to which natural selection should progressively eliminate the factors that reduce individual fecundity and fitness. Recently, however, Camperio Ciani, Corna, and Capiluppi (Proceedings of the Royal Society of London, Series B: Biological Sciences, 271, 2217–2221, 2004), comparing the family trees of homosexuals with heterosexuals, reported a significant increase in fecundity in the females related to the homosexual probands from the maternal line but not in those related from the paternal one. This suggested that genetic factors that are partly linked to the X-chromosome and that influence homosexual orientation in males are not selected against because they increase fecundity in female carriers, thus offering a solution to the Darwinian paradox and an explanation of why natural selection does not progressively eliminate homosexuals. Since then, new data have emerged suggesting not only an increase in maternal fecundity but also larger paternal family sizes for homosexuals. These results are partly conflicting and indicate the need for a replication on a wider sample with a larger geographic distribution. This study examined the family trees of 250 male probands, of which 152 were homosexuals. The results confirmed the study of Camperio Ciani et al. (2004). We observed a significant fecundity increase even in primiparous mothers, which was not evident in the previous study. No evidence of increased paternal fecundity was found; thus, our data confirmed a sexually antagonistic inheritance partly linked to the X-chromosome that promotes fecundity in females and a homosexual sexual orientation in males.” From the DISCUSSION: “Blanchard’s predictions were also confirmed in our study: we found that the homosexuals had an excess of older brothers compared with their own number of older sisters and compared with the heterosexuals’ number of older brothers. The homosexual and heterosexual groups did not differ with regard to the other three classes of siblings.” +++++++ Homosexuality clearly is caused by multiple factors, both genetic and environmental. It’s persistence in the species argues strongly that it provides some sort of reproductive advantage to those sharing the genes of the gay male involved. Remember that you are as closely related, genetically, to your nieces and nephews as you are to your grandchildren – sharing ¼ of your genes with both. Having more successful nieces and nephews is, reproductively, the same as having more successful grandchildren. Being gay may be a sign that your family line carries one significant genetic advantage over lines that do not have gay males.